Tektronix 2205 scope power problem

I'm apparently the not so proud owner of yet another broken oscilloscope. This time it's a Tek 2205 with a sick power supply section.

The eBay guide says that the 2205 is not a very wonderful scope:

"Stay away from the 2205, 2225 they were made in the orient, and have serious quality issues as used scopes." Oh well. At least it was free.

The outputs of all the various PS voltages are low (not zero). For example, the 250v line measures about 15VDC. I've checked all the big caps with an ESR tester and found nothing unusual or suspicious. When I first inherited the scope, the green pilot light came on but nothing else. By the time I got it open and started making measurements, the green pilot light went away. I disconnected all the various power supply connections (that conveniently run through 0 ohm jumpers) but the power supply lines still have low output, even with no load. I have a schematic and service manual.

However, I'm also lazy, have better things to break, and really don't know why I'm bothering to fix a 20MHz scope. Are there any common or chronic problems with the 2205 power supply section to check before I dive into the mess, rip it apart, and probably electrocute myself in the process?

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Jeff Liebermann     jeffl@comix.santa-cruz.ca.us
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558
Reply to
Jeff Liebermann
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Jeff Liebermann schrieb:

AFAIR the 2205 has a toroid transformer to set up a low DC of approx.

40 Volts and provides mains isolation. Folowed by a switchmode that converts the DC into all aother voltages needed in the 2205.

I's d recommend you look for a service manual, and follow the schematic.In my repairs the following: In the switchmode the usual suspects: caps, transistors, secondary HV multiplier. I don't know if bama has one for download, but it is worth a try.

hth, Andreas

Reply to
Andreas Tekman

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